As they are subject to vibrations, automobiles produce noises that are annoying for the occupants of the vehicle. Some of these noises are produced by the cables as they knock against the bodywork of the vehicle due to said vibrations. The vibrations can also lead to wear of the cables and, consequently, of the protecting tube.
In order to avoid such inconvenience, for some time now protecting tubes have been used which cover the cables of automobiles and absorb the noise.
These protecting tubes are made up of a braiding of filaments of plastic materials, which have the advantage of being highly elastic and of adapting to different cable diameters. In order to provide the protecting tube with the necessary noise-absorption characteristics, such tubes also include yarns of texturised material.
Patent ES-A-2.210.854, whose holder is the same as the applicant of this patent, discloses an isolating tube which is made up of different types of yarns, which permits a combination of elasticity and noise-absorption characteristics, together with resistance to abrasion and temperature.
As a result of increased wiring in automobiles due to the fitting of an ever increasing number of electrical and/or electronic appliances, the applicant has encountered a problem which was not known to date and which is the limited diameter of said protecting tubes.
The applicant has arrived at the conclusion that if protecting tubes of larger diameter could be manufactured, more cables could be passed through each tube, thus facilitating assembly of the electrical part of the automobile. However, with the present manufacturing machines, the manufacture of protecting tubes of larger diameter is not viable.
This impossibility is due to the fact that the present machines include a circular head provided with a plurality of needles. This head is surrounded by yarn guides which feed one yarn to each needle. On the basis of this machine, there is clearly a limitation of space for the number of yarns necessary for manufacturing tubes of large diameter. Furthermore, this machine is specially designed for manufacturing protecting tubes of small diameters, as this was so far considered to be the most suitable solution.
Warp knitting machines, such as the machines of the Raschel type, have been known for some time, but their field of application has lain outside the field of the automobile. Raschel machines are currently used for manufacturing various types of products, such as underwear or rugs.